The ALA section of the project attempts to automatically regulate the subjective loudness level of the input to a tuned, consistent level using a single gain stage and several input variables. Real-time gain regulation is calculated by the AlaControl and CompanderALA objects and gain is applied using the ALAgain object. It considers these input variables:
Input signal perceptual level
Current speed
Current entertainment volume setting
Tuned LUT’s which condition the control input signals
Current signal-to-noise in the cabin as computed by the NoiseEst object
The ALA section of the project operates in the following way:
The Merger object passes a combined (mono) signal to the CompanderALA object
The signal is band-passed first by the BiquadsPreFilter object
The CompanderALA object computes a final gain value to send to the ALAgain object, based on current signal level plus input from the AlaControl object
The NoiseEst object generates a measure of signal-to-noise ratio using a cabin microphone signal compared with current entertainment audio
The AlaControl object receives control signals from the LUT’s and NoiseEst and regulates the CompanderALA object accordingly
The ALAgain object applies the final gain value to the input signal
The CompanderLevel object is a level monitor which allows the user to monitor the ALA gain